WASHINGTON — More than four out of five police agencies in the U.S. have no written policies for handling eyewitness identifications despite long-standing federal guidelines, according to a report obtained by USA TODAY.

The findings in the National Institute of Justice report, come as flaws in eyewitness identification represent the single greatest cause of wrongful conviction, contributing to 75% of convictions overturned through DNA testing, according to the Innocence Project, which uses DNA testing to challenge criminal convictions. More than 300 people have been exonerated since 1989 through post-conviction DNA testing.

The report, which was produced for the Justice Department's research arm by the Police Executive Research Forum, is the first national assessment of eyewitness identification standards. In it, 84% of police agencies reported that they had no written policy for conducting live suspect lineups, and slightly more than 64% said they had no formal standard for administering photo displays of potential suspects.

Though witnesses always have been an integral part of criminal investigations, there has been "growing recognition" that eyewitness identifications are often unreliable, according to the NIJ report. Some of the problems have been associated with faulty memories of specific incidents and unwitting or undue influence exerted by authorities investigating the crimes.

"When the credibility of the criminal justice system is being subject to legitimate questions, this is one issue we really need to get right," said Chuck Wexler, executive director of the research forum whose group compiled data from 619 police agencies over 15 months. "The procedure (for eyewitness identification) clearly hasn't received the rigorous study that it needs."

Police agencies reported the lack of standardization despite 1999 National Institute of Justice guidelines that urged law enforcement to improve policies for how witnesses are used to identify suspects.

The guidelines emphasized the benefit of "blind" testing in lineups — that is, lineups conducted by administrators who do not know the identities of the suspects, avoiding improper influence. But the report found that nearly 70% of police agencies still use officers with knowledge of the suspects in photo lineups, and 90% of agencies use "non-blind" administrators in live lineups.

The problems, according to the report, are especially persistent in small agencies. But even in large agencies — with 500 or more officers — 25% reported no policies for conducting photo lineup presentations, and fully half of the responding agencies had no policies for live lineups.

"It is important for police and other justice system officials to exercise caution when using eyewitness identification evidence, particularly in cases were an eyewitness identification is the sole evidence of guilt," the report concluded.

Barry Scheck, co-director of the Innocence Project, characterized the findings as "extremely disturbing."

"These findings are actually worse than we thought they would be," Scheck said, adding that at a minimum, law enforcement agencies should ensure that lineups are being administered by officers who do not know the identity of the suspect to guard against intentional or unintentional influence.

"When you don't know who the suspect is, you are going to get a better answer," he said. "All of the major police organizations have agreed that these best practices not only protect the wrongfully convicted, but they also protect the police."

For lineup standards advocates, David Wiggins' wrongful conviction in 1989 in the sexual assault of a 14-year-old child represents a real-life casualty of a flawed system.

Detained on an unrelated case, Wiggins volunteered to participate in a live lineup, believing that he could "clear up any confusion and everything would be all right."

"That ain't the way it went," said Wiggins, who spent 23 years in prison for the crime before he was exonerated last October.

While viewing a photo array, the young victim, whose face was covered during much of the attack, said Wiggins looked familiar. Wiggins was placed in a live lineup, the only potential suspect included in the live lineup from the previous photo display.

Wiggins' attorney did not challenge the lineup procedures, which were not administered under "blind" conditions, according to the Innocence Project. The attorney did not offer expert testimony to question the identification.

"At trial, they (prosecutors) made it look so good, I felt guilty," said Wiggins, who was later exonerated with the assistance of DNA testing.

"I don't blame her," said Wiggins, who has met with the victim since his release. "She said, 'I feel guilty.' I told her it was all right and that it didn't change the fact that she was a victim."